The rate of reaction of heme complexes with molecular oxgen will be investigated in aqueous solution in the presence and absence of micelle-forming surfactants. The dependence of the oxidation rate on pH and ligand type concentration will be determined and interpreted in terms of the mechanism of the reaction. The effect of hydrophobic environment on the stability of heme complexes toward oxygen will be examined in order to clarify the nature of protein-heme interactions in oxygen-carrying proteins.